A display screen on electronic devices can show various types of information to users, such as text, picture, or video. Generally, liquid crystal displays use light emitting diodes as backlight source. Pixels of the display screen may tend to uneven brightness as the backlighting scatters at the edge of the display screen, or because of the high brightness of the light emitting diode itself. To resolve the problem, a black plastic frame can be employed to improve the brightness uniformity of the display screen, but this can result in an overall brightness decrease.